1. Field of the Invention
The present invention relates to an endoscopic device, and more particularly, to an endoscopic device having means for controlling the brightness of an image generated based on an image pickup signal outputted from an endoscope.
2. Description of the Related Art
An endoscopic device having an endoscope, a light source device, and the like has been conventionally widely used in the medical and other fields. Examples of generally known observations using the endoscopic device in the medical field include a normal observation of directing white light to a subject in a living body and then picking up an image of the subject substantially similar to visual observation and a narrow band imaging (NBI) of directing a narrow-band light to the subject, the light having a band narrower than the illumination light in the normal observation, to observe the subject, thereby allowing to pick up an image of a blood vessel of a superficial portion of the mucous membrane in the living body and the like, with an excellent contrast as compared to the normal observation.
With narrowing down of the band, the narrow-band light used in the narrow band imaging is emitted to a subject in a state with less light intensity compared to the illumination light used in the normal observation. Therefore, in the narrow band imaging, a control is necessary for amplifying and adjusting the brightness of the image based on the image of a subject picked up by the endoscope. Endoscopic devices that perform the above control are proposed, for example, in Japanese Patent Application Laid-Open Publication No. 07-136107 and in Japanese Patent Application Laid-Open Publication No. 2002-095635.
Even when an image with a desired brightness cannot be obtained with control to the light source device because the light intensity adjustment of the light control circuit is out of the range, the endoscopic device proposed in Japanese Patent Application Laid-Open Publication No. 07-136107 is configured to be able to obtain an image with a desired brightness by applying the gain adjustment of a video signal to a video processor.
The endoscopic device proposed in Japanese Patent Application Laid-Open Publication No. 2002-095635 is configured to be able to obtain an image adjusted to include an appropriate S/N in the narrow band imaging by increasing or decreasing the voltage level of the driving voltage of the lamp in accordance with the timing of the emission of the illumination light in each band included in the narrow-band light.